This is an investigator-initiated evaluation of the renal and neurohormonal effects of the first oral nonpeptide V2 receptor vasopressin antagonist available for clinical research in the united states. The study, set up as a collaborative effort with the gcrc at the university of iowa investigates the role of vasopressin in the renal water retention of heart failure. Preliminary data are encouraging and will be presented at the American College of Cardiology 46th Annual Scientific Session in March 1997.